Abstract: A projection exposure apparatus includes an illumination optical system for illuminating a pattern formed on a first object, with light, a projection optical system for projecting the pattern of the first object, illuminated by the illumination optical system, onto a second object for exposure of the same with the pattern, a main system including the illumination optical system and the projection optical system, and an interferometer for use in measurement of an optical characteristic of the projection optical system and being mounted on the main system.

Abstract: A device for measuring depth of a groove formed on an article includes a light source for illuminating the article, a first detector for receiving light from a portion of the article having a groove and being illuminated by the light source, and for detecting a spectral reflectance in relation to the received light, a second detector for receiving light from the article illuminated by the light source and for detecting a spectral reflectance in relation to the received light, the second detector being effective to detect the spectral reflectance in a way not affected or substantially not affected by the groove of the article as compared with the detection by the first detector, and a depth detector for detecting the depth of the groove on the basis of the results of detection by the first and second detectors.

Abstract: Fabri-Perot spectroscopy method comprises a step of directing a light beam at a first refraction angle to a first Fabri-Perot interference plate and a step of directing a light beam transmitted through the first Fabri-Perot interference plate to a second Fabri-Perot interference plate at a second refraction angle, and Fabri-Perot spectroscopy apparatus comprises Fabri-Perot interference plates, a control device for changing a spacing between the Fabri-Perot interference plates, a first optical device for directing a light beam to the first Fabri-Perot interference plate at a first refraction angle, a second optical device for directing the light beam transmitted through the Fabri-Perot interference plate at a second refraction angle different from the first refraction angle to the second Fabri-Perot interference plate, and a seal for externally sealing the Fabri-Perot interference plates. Gas for protecting the Fabri-Perot interference plates is filled in the sealed space.